The prior art is already aware of palletizing items which are in a block form, such as a bundle of sheets, and the common way of accomplishing this is to manually stack the bundles of sheets in layers and rows on a pallet. In a broader sense, the prior art also is aware of utilizing pickup devices and overhead cranes for handling box-like items which can be stacked onto pallets. The present invention involves use of a pickup mechanism for a bundle of sheets and having that mechanism attached to an overhead crane which transports the bundle of sheets to a specific location on a pallet underneath the overhead crane, such that a single pickup station is utilized but the various bundles are placed in respective positions on the pallet to form layers and rows of the bundles on the pallet.
Palletizing or other movement of bundles or the like is shown in U.S. Pat. Nos. 3,612,300 and 3,757,966 and 3,901,392 and 4,083,461 and West German Pat. No. 18,354 and West German Pat. No. 2,213,120 and West German Pat. No. 2,721,675; also see U.S. Pat. No. 4,419,035.
The present invention improves upon and differs from the prior art in that it provides for a simplified overhead crane type of structure which picks up a bundle of sheets at a first position and moves the bundle of sheets directly to a palletizer where the sheets are placed in layers and stacks in respective positions. In accomplishing this, the overhead conveyor or crane is of an endless conveyor construction where the conveyor continuously moves around support members, such as pulleys, and in given directions so that the conveyor can be operated with a simplified drive mechanism which accomplishes the uni-directional drive to the endless conveyor. Therefore, the endless conveyor picks up the bundle of sheets and elevates them and then moves them horizontally to the position on the pallet, and the conveyor then continues in its previous direction to ultimately reverse its direction and return to the pickup station for the next bundle.
Further, the present invention differs from the prior art in that it provides for electric means which initially position the pickup mechanism at the pickup station and which then elevates the gripped bundle and moves it horizontally to a position relative to the pallet where the bundle is lowered by an elevator means independent of the overhead crane itself. In that regard, the overhead crane is of a simplified construction and is continuously driven in its one endless manner, as mentioned, and only the elevator means is operated for lowering and depositing the bundle on the pallet.
In further distinction over the prior art, the present invention provides for operating an electric pickup means at the pickup station for initially elevating the bundle, and then utilizing the photo-electric cell for controlling the height of the pallet and utilizing another photo-electric cell for positioning the elevated bundle relative to the pallet, and then finally operating an elevator means which lowers the bundle onto the pallet and does so independent of the operation of the overhead crane itself. In this regard, only one overhead crane drive is required since the crane moves in its continuous and endless manner, such as mentioned.